The present invention relates to a new and improved method of, and apparatus for, measuring the moisture content or dampness of flat textile structures, especially textile webs.
The heretofore known textile moisture regulators which perform moisture measurements according to a conductance measurement principle only can fulfill their function in a limited fashion, especially since the advent of synthetic textile fibers. Thus, the conventional input circuit, constituted by a voltage divider composed of the oftentimes extremely high current-flow resistance of the textile web to be measured and a limited high ohm fixed resistor, no longer furnishes any practically usable signal evaluation at voltage divider ratios greater than approximately 1:100 and 100:1.
The resistance values up to about 10.sup.12 ohms which are conventional for synthetic textiles lead to voltage divider ratios which are larger by a number of decades than the indicated values. Also a corresponding increase of the fixed resistance of the aforementioned voltage divider, as a general rule, is hardly possible due to the limited insulation properties of the insulation material which is employed and the input resistance of the required measuring amplifier.
Apart from these limitations of the measurement range, there are also present disturbance effects caused by external voltages, thus, for instance, due to electrostatic charges especially present in the case of textile webs formed of synthetic fibers, but furthermore also due to noise or hum. Fault currents, caused by such external voltages, are often of the same order of magnitude or even greater than the measurement currents of a number of picoamperes which are standard in the case of dry, synthetic textiles and thus render impossible reliable measurement of such materials.